So I drove it home, so very very pleased. It sounded awesome, popped and banged on the over-run, turned heads everywhere and all in all was a gorgeous drive.
I gave it some boost going down the road but it seemed a little slow, a little hesitant... I could only assume that as my s2000 was 550hp, this obviously wasn't going to feel as quick. So carried on driving it regardless.
I noticed that half of the dash gauges didn't work (he told me this when showing me round it) but now I got to have a closer look. The voltage gauge was reading off the scale with the charge lamp on constantly... I thought nothing of this as I he told me it wasn't wired up to the gauge so was showing incorrect readings.
Oil temp didn't work, coolant temp didn't work, rev counter didn't work... all making sense as the sensors were not hooked up or indeed calibrated for those gauges. Only the fuel gauge worked, this only worked upto half way though.. above half a tank doesn't show on the gauge.
Anyways... fast forward to a few weeks later (only driven the car once more since collecting it) and I pull up at my garage to hear a hissing noise (kind of like a someone letting air out of the tire) On closer inspection I hear that the hissing noise is coming from the engine bay. I think possible coolant leak? Pressure escaping etc? I open the bonnet (Hood in your case) to find that the battery is swollen like a balloon and the hissing is coming from there!! I managed to open one of the battery caps and release the pressure. Checked the voltage and its kicking out 17.5v at idle! RIP BATTERY!
Found out the external regulator was still connected to the car and the SR20 alternator runs an internal one. A few days of wiring checks, regulator rewire etc etc turns out the alternator voltage regulator is dead anyways, so no difference made there
New Nissan Serena alternator purchased (90A) to replace the dead one. Mounting holes seem to match up even though the plugs and power are in slightly different locations, but no worries as everything will reach!
So whilst the alternator is out of the car, I decided to replace the restrictive "turbo elbow" that comes on the SR20. OF COURSE the manifold studs were going to be seized and come out of the head.. why wouldnt they? Had to be re-tapped, so new studs and nuts ordered!
Oh and I think I found why the car seemed a bit sluggish.... exhaust leak city.
Now onto the turbo... that's right you guessed it... TURBO STUDS SEIZED TOO. Out they come, turbine housing re-tapped and new ones put in their place.
Whilst all this is off, I looked at the current exhaust.. It was a miss-mash of old parts. 3 inch tubing bashed in places to fit around the r200 diff. A supra back box that the PO had laying around so decided to use on the Datsun. My friend who's into fabricating his own parts took one look at it and said he couldn't let it stay like that. So he gave me a shopping list and told me to go do a buy. He decided that he was going to fabricate me a custom exhaust which goes up and over the rear axle. It's still a work in progress but here's the back box...

Hey all,
Firstly thanks for clicking on my build thread and taking the time to read/look at the pictures.
So where do I start, if you read my new members post you will see I picked up this 280z from a friend in a trade deal whereby I swapped my home built s2000 turbo (some say I'm crazy to get rid of it but bah, what the hell.. I knew the s2000 was going to a good home and I love old Z cars.)
Here it is when I went round to view it at my friends house... I instantly fell in love...
I knew I just had to have it!
It already had the SR20DET swap which is a little rough round the edges, but in the PO defence, he had 28 day warranty on the engine so had to get it into the car as soon as he could to make sure it checked out OK. This wasn't long after he had it all up and running.
I drove home that night with a huge smile on my face knowing I would be a Z car owner!! My dream car was going to be mine.
So the day came to swap the cars, here is an image of the 2 cars together..

Ok so... after getting it fixed and not driving it since, took it out for a drive and sure enough the OEM alternator regulator was goosed.
14.5v at idle, but rises to 18v when going through the rev range.
Replacing it with a new one from a Nissan Serena which is a 90amp alternator.
Connectors are in a different place, but the mounting holes seem to be identical. Hopefully getting it mounted up this weekend so will report back when changed. Would ideally love to keep the charge lamp of the OEM loom. Seems the car seriously needs the wiring stripping out and starting again.

Thanks for the heads up buddy!
I will leave the car sitting for a few days and see what happens to the battery. I have a jumper pack ready just incase.
I also noticed that my car has the "brake" lamp on constantly. I have checked the fluid and the handbrake switch and all seem to be good. Strange one!

OK today's update...
So turns out the PO who did the conversion, didn't remove the external voltage regulator!!!
I followed AtlanticZ external to internal regulator conversion and sure enough, the OEM regulator was still there. Disconnected the 6 pin plug, started the car and voltage at idle is now 14.5V!
I will however be wiring the new alternator into the OEM loom to utilize that charge lamp on the voltmeter.
Hopefully this helps anyone else taking on a project! Thanks for your help NewZed. Props!

Thanks for the diagram! Makes things a little clearer... so after some thinking, I'm not even sure that the "lamp" that's currently hanging under the steering column has a resistor on it! That may be the source of the problem right there!

I don't understand how the charge light is on as the alternator is not connected to the existing loom in any way shape or form...
Its a stock sr20 alternator so the wiring should match the guides, but I totally agree, start from scratch with the wiring and voltmeter.

Ok so... the alternator isn't wired into the 280z loom at all so there could be an issue there somewhere.
The conversion and wiring was done by the previous owner so I'm trying to work out whats going on.
The bulb under the steering column is an aftermarket one (Dont think the S30 had this) and the red LED I refer to is the stock voltage gauge in the dash pod which I dont how its working and showing as charging? Something very strange going on here....

****ADMINS PLEASE MOVE TO NISSAN FORUM****
Hi all, hoping to nail the electrical issue I'm having...
280z SR20DET swapped.. alternator is outputting 17.5v at idle to the battery and has caused the battery to swell and leak all over my bay!!
I have the wiring as follows... Large charging cable direct to battery, yellow wire direct to battery with 10amp fuse, Red/White wire to a bulb under the steering column.
Bulb illuminates with ignition on, engine starts, bulb goes out (so I'm guessing all that side is good) Dash gauge shows red charging LED illuminated and the voltage is off the scale.
My bulb holder has a small moment switch on the back of it, so with that held in alternator is basically switched off and battery voltage drops to 12.8v (same as engine off)
Am I missing something here? Everything seems to be wired in properly.. only thing I can think is the regulator on the alternator is shot and a new alternator is required.
Many thanks for your advice.

Here is an image from side on for a better angle. They do look slightly low. May have to realign them then! Not sure if they are cheap copies or a decent fitting set. I'll have a search and find the over fender fitting guide.

Yes sir, genuine devil shadow wheels from Japan.
I did think that when I saw them. And the fronts too! Thought they were supposed to line up with the crease at the bottom of the door/sill.
Thanks for the heads up. The rear splitter will be removed too.